Vancomycin's half life of the terminal phase is significantly prolonged in the elderly from young normals. No significant change was observed in volume of distribution which could be accounted for by altered tissue binding. Zimelidine, a serotonergic reuptake blocker, was evaluated in Alzheimer's disease patients. Pharmacokinetic, neurochemical and neuropsychological effects were examined. The drug significantly reduced (by up to 38%) 5-hydroxy-indolacetic acid concentrations in cerebrospinal fluid (CSF). CSF concentrations of 3-methoxy-4-hydroxy-phenylglycol, a major metabolite of norepinephrine, tended to increase slightly. Overall, there was no effect of Zimelidine on memory function.